#include <iostream>
#include <string>
#include <regex>

int main()
{
    std::string str = "Hello/12345";
    std::regex pattern("Hello/(\\d+)");
    std::smatch matchs;
    bool ret=std::regex_search(str,matchs,pattern);
    if(ret==false)
    {
        std::cout << "No match" << std::endl;
        return -1; 
    }
    for(auto &s:matchs)
    {
        std::cout << s << std::endl;
    }
    return 0;
}